Gum inhibitor for hydrocarbons



Mi s... 19, 1933 .T

PATENT OFFICE UNITED s rs rss your! mnmrroa roa nrnaocaaaons William 8.Calcott, Penna Grove, N. 1., and Herbert W. Walker, Wilmington, DeL,asslgnors to -E.I.; du Pont-ude Nemours & Company, Wilmington, DeL, acorporation of Delaware m Drawing. Application September rs, ms

, Serial No. assess 6 improved for use with-unsaturated liquidhydrocarbons which may be used as fuels. 4 Liquid hydrocarbons ascommercially produced,.

particularly when prepared bythe distillation or cracking of petroleum,possess a tendency to dis- 1 coloronstandingandtoformgumsandresinous'substances. Gasolines produced by the modern cracking processes areextremely comm mixtures comprising many constituents, thecharester ofthese constituentsa'nd the relative proportions of differentconstituents depending upon the source of the crude and the particularcrack ing process employed. Besides the and branched chainparaflineajthere are often present substantial percentages of aromatichydrocarbons. 2 The crude cracked gasoline also always containsunsaturated hydrocarbons, such for example as oleflnes and diolennes.Although there may be present some compounds containing a triple bond,

theseareprobablynot compoundssuchasmay be 2 formed by thepolymerisationof acetylene, but rather such compounds as maybe formed bythe isomerimtion of dienes and having the general formula CnHm where mis greater than a, but

less than n+2, These unsaturated compounds in the presence of air arecapable of oxidation to form a series of products, some of which areresinous or gummy. The dioleiines, and more unsaturated hydrocarbons,are particularly easily oxidized. Diiferencesin structure other than the36 degree of unsaturation cause considerable variation in the tendencyto oxidize, but in general the 1 case of oxidation increases withthedegree of unsaturation. The more recent pressuremethods of vaporphase cracking result in a considerably 4 higher percentage ofdioleiines than the older methods, and it has been stated thattheseproductsmayrunashigh asato' 15%.inunreiined gasoline.

It has been necessary to treat the crude products resulting from themore recent cracking processes in some manner to remove the greater partof these more highly unsaturated products. Among these methods oftreatment may be mentioned the sulfuric acid treatment and the fullersearth vapor phase treatment. While these methods of purification mayremove the greater part of the highly unsaturated compounds, it is foundthat many brands of gasoline tend to discolor on storage and totform acertain amount of gum.

'lhegmnappearstobeacomplexmixtureof polymerized hydrocarbons, resins,acids, aldehydes, ketones and peroxides. Its formation .is distinctlydetrimental in all cases. For example, the deposition of gum in gasolinegives a sticky substance which deposits upon the walls and bottomof thecontainer, and which may cause serious .trouble if formed or depositedin the fuel system of internal combustion engines. The solubleportion-of the gum is also objectionable because of the introductionof'a non-volatile component into 66 the gasoline; T

Our invention has foran object the inhibition of the formation of theseinsoluble gums and resins, with an attendant improvement in the qualityof the hydrocarbon and freedom from the 70 dimculties introduced by theformation of the more or less insoluble and sticky. gummy material, suchas irregular flow in the fuel and lubricating systems of internalcombustion engines. A further object is to make it possible to use as aninternal combustion fuel, liquid hydrocarbons such as gasoline, thatcontain larger amounts of highly unsaturated compounds than commerciallyused at present. A product of this sort can be produced at a lower cost,and possesses in certain cases, improved anti-knock properties.

We have found that by treating hydrocarbons, and specificallyunsaturated hydrocarbons such as hydrocarbon fuels, and morespecifically such as cracked gasoline or gasoline which has a tendencyto form gum, the gum formation can be very appreciably inhibited if thehydrocarbon is treated with a diaryl guanidine salt of a fatty acid.More specifically, our invention relates to the use as gum inhibitorsfor hydrocarbons of compoundsofthetype in which A is a fatty acid and inwhich R is an aryl group, and R is an aryl group which may be the sameas or diiferent from R, and in which both R and B. may contain alkylsubstituents. By way of illustrating our invention, we may set 1 0 forththe following examples:

Examplef Diorthotolylguanidine-stearate was dissolved to the extent of0.002% in an unstable gasoline sunlight exposure test was made with asample treated with diorthotolylguanidine-stearate, and it was observedthat a sample remained essentially colorless and contained no gumresidues after three weeks exposure to sunlight.

Example 2 During a sunlight exposure test, using glass bottles, agasoline sample treated with 0.002% diphenylguanidine butyrate, theproduct obtained by mixing 1 mol of diphenylguanidine and 1 mol ofbutyric acid, remained colorless and free from insoluble gums for threeweeks time, whereas yellowing and gum formation occurred to a verymarked extent in a check sample of the same gasoline containing no guminhibitor. The diphenylguanidine butyrate obviously gave protectionagainst discoloration and gum formation.

Throughout our specification by fatty acid we mean mono-carboxylic acidderivatives of an aliphatic hydrocarbon such as, for example, propionic,palmitic, acetic, butyric, stearic, oleic acids, and the like. Withinthe contemplation of our invention will be found salts formed bycombining such fatty acids with diaryl guanidines such as, for example,diparatolyl guanidine, dixylyl guanidine, phenyl tolyl guanidine,dialpha-naphthyl guanidine, diortho anisyl guanidine, as well asdiorthotolyl guanidine and diphenyl guanidine.

In some cases it has been found advisable to use the acid salt of amixture of guanidines rather than a single pure product. Conversely, asingle guanidine or one or more guanidines may be combined with amixture of fatty acids falling within the class described above. Theformation of the fatty acid salt of the guanidines may be made, forexample, by a process similar to that described in U. S. Patent1,747,187 to Winfield Scott. It has been found, in some cases, that acombination of two different guanidine salts is superior in its effecton gasoline to either guanidine salt used singly. In general, however,we prefer to use the fatty acid salt of diorthotolyl guanidine andspecifically the stearic acid salt of ditolyl guanidine, which is theproduct formed by fusing 1 mol of stearic acid with 1 mol ofdiorthotolyl guanidine. We may use higher or lower concentrations of anymembers of the class of compounds represented by the general formulagiven hereabove to secure marked inhibition of gum formation, although,of course, the degree of inhibition will vary depending upon theindividual guanidine salt, the concentration of guanidine salt employed,and the nature of the hydrocarbon fuel. In general, the concentration ofinhibitor may vary from 0.00025 of 1% to .01 of 1% or higher, dependingupon the nature of the gasoline, the storage conditions, the length oftime protection is desired, and the specific inhibitor being used. Itwill be obvious, of course, that these percentages may be varied withinwide limits.

Clearly, our invention is of great importance in freeing internalcombustion engines from the annoyance and improper functioning due tothe deposition of gum in the fuel system and explosion chamber. However,it is to be understood that our invention is not limited to the guminhibition in gasoline fuels. Other hydrocarbon fuels and otherhydrocarbons may be effectively treated with our class of guminhibitors. Thus, transformer oils, lubricating oils and unsaturatedhydrocarbons containing oleflnes and dioleiines are susceptible totreatment.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit thereof, it is to be understoodthat we do not limit ourselves to the foregoing examples or descriptionsexcept as indicated in the following patent claims.

We claim:

1. Gasoline normally tending to form gum, to which has been added, insufilcient amount to inhibit the formation of gum, a diaryl guanidinesalt of a fatty acid.

2. Gasoline normally tending to form gum, to which has been added, insufficient amount to inhibit the formation of gum, a diaryl guanidinesalt of a fatty acid from the group comprising acetic, butyric,propionic, palmitic, stearic and oleic acids.

3. Gasoline normally tending to form gum, to which has been added, insufllcient amount to inhibit the formation of gum, a compound of the ypNHR' AHN- =C/ NHR in which A represents a fatty acid, and R an arylnucleus, and R an aryl nucleus which may be, although not necessarilyis, the same as R and in which, as in R, there may be alkylsubstituents.

4. Gasoline normally tending to form gum, to which has been added, insufllcient amount to inhibit the formation of gum, a compound of thetype in which A is a fatty acid from the class comprising acetic,butyric, propionic, palmitic, stearic and oleic acids, and R an arylnucleus, and R an aryl nucleus which may be, although not necessarilyis, the same as R and in which, as in R, there may be alkylsubstituents.

5. Gasoline normally tending to form gum, to which has been added, insuillcient amount to inhibit the formation of gum, a diorthotolylguanidine salt of a fatty acid. 1

6. Gasoline normally tending to form gum, to which has been added, insufficient amount to inhibit the formation of gum, a diorthotolylguanidine salt of a fatty acid from the class comprising acetic,butyric, propionic, palmitic, stearic and oleic acids.

7. Gasoline normally tending to form gum, to which has been added, insufficient amount to inhibit the formation of gum, the diorthotolylguanidine salt of stearic acid.

8. Gasoline normally tending to form gum, to which has been added, insuillcient amount to inhibit the formation of gum, adiphenyl guani-

